1. Field of the Invention
The present invention relates to an ultrasonic vibration bonding machine for bonding a plurality of members which are placed one upon another with ultrasonic vibration.
2. Description of the Prior Art
As disclosed by Japanese Laid-open Patent Application No. 10-22308, the Applicant proposed an ultrasonic vibration bonding machine for bonding a plurality of members which are placed one upon another with ultrasonic vibration.
When a plurality of members which are placed one upon another are to be bonded together by the above ultrasonic vibration bonding machine, the following bonding failures may occur according to the sizes of portions to be bonded together and the physical properties of their materials and the like: the bonded portions are pressed excessively when pressure applied to these portions of the plurality of members placed one upon another is too strong, or the bonded portions are separated from one another when pressure is too weak.
To cope with these, the present invention provides an ultrasonic vibration bonding machine which enables appropriate bonding by selecting a pressure curve according to the sizes of portions to be bonded together and the physical properties of their materials and the like.
According to a first aspect of the present invention, there is provided an ultrasonic vibration bonding machine for bonding a plurality of members placed one upon another with ultrasonic vibration by pressure holding the plurality of members between a resonator supported by a bonding unit and the mount table of a mounting unit and transmitting ultrasonic vibration to the resonator from a transducer connected to the resonator, wherein the bonding unit comprises a vertical drive unit for bonding work and a pressure control unit for bonding work.
According to a second aspect of the present invention, there is provided an ultrasonic vibration bonding machine, wherein the vertical drive unit moves the resonator toward the mount table side of the mounting unit, and the pressure control unit selects pressure for a time interval from the time when the plurality of members placed one upon another are held between the resonator and the mount table to the time when they are bonded together with ultrasonic vibration according to the sizes of portions to be bonded together and the physical properties of their materials and the like. Thereby, the plurality of members placed one upon another are bonded together properly without being pressed excessively or separated from one another.
According to a third aspect of the present invention, there is provided an ultrasonic vibration bonding machine, wherein the bonding unit is composed of a motor and a bolt-nut unit connected to the output shaft of the motor and a holder supporting the resonator. Compared with the case where the bonding unit is composed of a cylinder which moves only linearly, the bonding unit converts rotary motion into linear motion, thereby making it easy to control the speed of the vertical movement of the resonator.
According to a fourth aspect of the present invention, there is provided an ultrasonic vibration bonding machine, wherein the pressure control unit is composed of an air cylinder connected to the output end of the bonding unit and a holder supporting the resonator. Compared with a pressure control unit which is composed of an element other than the air cylinder, the pressure control unit can adjust pressure applied to the plurality of members placed one upon another with air which is a compressed elastic fluid.
According to a fifth aspect of the present invention, there is provided an ultrasonic vibration bonding machine, wherein the pressure control unit comprises a pressure supply system for supplying pressurized air to an equilibrium chamber and a pressure chamber formed in the air cylinder and setting means for setting the pressure of pressurized air to be supplied from the pressure supply system to the equilibrium chamber according to the total weight of elements connected to the pressure control unit and the pressure of pressurized air to be supplied from the pressure supply system to the pressure chamber according to the sizes and materials of members to be bonded together. Therefore, the pressure control unit can set pressure control conditions such as a vibration start pressure set value, first pressure set value, second pressure set value and equilibrium pressure set value.
According to a sixth aspect of the present invention, there is provided an ultrasonic vibration bonding machine, wherein a load sensor is provided on a holder supporting the resonator. Therefore, the total weight of the elements supported by the pressure control unit can be detected accurately and does not need to be calculated.
The above and other objects, features and advantages of the invention will become more apparent from the following description when taken in conjunction with the accompanying drawings.